position-sticky-nested-top.html

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This WPT test may be referenced by the following Test IDs:
- /css/css-position/sticky/position-sticky-nested-top.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>Nested top-constrainted position:sticky elements should render correctly</title>

<link rel="help" href="https://www.w3.org/TR/css-position-3/#sticky-pos" />

<meta name="assert" content="This test checks that nested position:sticky elements with a top constraint render correctly" />

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<script src="../resources/sticky-util.js"></script>

<body></body>

<script>

test(() => {

  const elements = setupNestedStickyTest('top', 50, 60);

  elements.scroller.scrollTop = 100;

  const nonStickyTopY = elements.container.offsetTop +

      elements.filler.clientHeight;

  assert_equals(elements.sticky.offsetTop, nonStickyTopY);

  // The inner sticky should not be offset from the outer.

  assert_equals(elements.innerSticky.offsetTop, 0);

}, 'before reaching the sticking point, neither sticky box should be offset');

test(() => {

  const elements = setupNestedStickyTest('top', 50, 60);

  elements.scroller.scrollTop = 145;

  const nonStickyTopY = elements.container.offsetTop +

      elements.filler.clientHeight;

  assert_equals(elements.sticky.offsetTop, nonStickyTopY);

  assert_equals(elements.innerSticky.offsetTop, 5);

}, 'the inner sticky can stick before the outer one if necessary');

test(() => {

  const elements = setupNestedStickyTest('top', 50, 60);

  elements.scroller.scrollTop = 200;

  // This math cancels to sticky.offsetTop == (scroller.scrollTop + 50), but

  // for clarity the calculations are left explicit.

  const nonStickyTopY = elements.container.offsetTop +

      elements.filler.clientHeight;

  const targetTopY = elements.scroller.scrollTop + 50;

  const stickyOffset = targetTopY - nonStickyTopY;

  assert_equals(elements.sticky.offsetTop, nonStickyTopY + stickyOffset);

  // The inner sticky has similar math, but its offsetTop is relative to the

  // sticky element and in this test is the difference between the top values.

  assert_equals(elements.innerSticky.offsetTop, 10);

}, 'both sticky boxes can be stuck at the same time');

test(() => {

  const elements = setupNestedStickyTest('top', 50, 60);

  elements.scroller.scrollTop = 300;

  const maxOffsetInContainer = elements.container.offsetTop +

    elements.container.clientHeight - elements.sticky.clientHeight;

  assert_equals(elements.sticky.offsetTop, maxOffsetInContainer);

  const maxOffsetInOuterSticky = elements.sticky.clientHeight -

      elements.innerSticky.clientHeight;

  assert_equals(elements.innerSticky.offsetTop, maxOffsetInOuterSticky);

}, 'neither sticky can escape their containing block');

test(() => {

  const elements = setupNestedStickyTest('top', 50, 300);

  elements.scroller.scrollTop = 100;

  // The outer sticky has not stuck yet.

  const nonStickyTopY = elements.container.offsetTop +

      elements.filler.clientHeight;

  assert_equals(elements.sticky.offsetTop, nonStickyTopY);

  // But the inner sticky still cannot escape the outer sticky (as it is the

  // containing block).

  const maxOffsetInOuterSticky = elements.sticky.clientHeight -

      elements.innerSticky.clientHeight;

  assert_equals(elements.innerSticky.offsetTop, maxOffsetInOuterSticky);

}, 'the inner sticky cannot be pushed outside the outer sticky');

</script>